felipecrv commented on code in PR #43256:
URL: https://github.com/apache/arrow/pull/43256#discussion_r1700408684
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cpp/src/arrow/compute/expression.cc:
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@@ -1242,8 +1273,92 @@ struct Inequality {
/*insert_implicit_casts=*/false, &exec_context);
}
+ /// Simplify an `is_in` value set against an inequality guarantee.
+ ///
+ /// Simplifying an `is_in` predicate involves filtering out any values from
+ /// the value set that cannot possibly be found given the guarantee. For
+ /// example, if we have the predicate 'x is_in [1, 2, 3, 4]' and the
guarantee
+ /// 'x > 2', then the simplified predicate 'x is_in [3, 4]' is equivalent.
+ /// This can be done efficiently if the value set is sorted and unique by
+ /// binary searching the inequality gound and slicing the value set
+ /// accordingly.
+ ///
+ /// \pre `guarantee` is non-nullable
+ /// \pre `guarantee.bound` is a scalar
+ /// \pre `guarantee.bound.type()->id() == value_set->type_id()`
+ /// \pre `value_set` is non-empty
+ /// \return a simplified value set, or a bool if the simplification results
in
+ /// a boolean literal predicate.
+ template <typename ArrowType>
+ static std::variant<std::shared_ptr<Array>, bool> SimplifyIsInValueSet(
Review Comment:
You can return a value that indicates the simplification should be aborted.
This is a common difficulty in kernel development: specializing by type
(using templates) only the kernel loops (in this case, the loop is the
binary-search) so that binary size doesn't explode.
<!-- Other libraries don't care so much about binary size, but Arrow's
success as a basic dependency on so many libraries comes from not being a
multi-GB library like many template-heave compute kernel libraries can be. -->
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